Wear-resistant surfaces are a critical component of many applications. For example, fluid catalytic cracking in petroleum refineries employ “catalyst risers,” vessels which undergo severe internal wear from hard ceramic catalysts. Also, paper manufacturing, metal production, and mining rely on rolling processes to form a variety of materials into a desired shape, form, or condition. These processes require the roller to possess wear-resistant surfaces. Because it is common for hardfacing surfaces and ceramic tiles used in such high-wear applications to eventually crack, the surface can rapidly deteriorate, resulting in failure and, consequently, requiring shutdown of the operation and lengthy repair of the hardfacing surface, if repair is even possible.
Typically, the desired characteristics are imparted to the wear-resistant surface by applying a coating or surface treatment directly to the inside of the vessel or to the surface of the roller. Common processes for applying the coating or surface treatment include welding, plating, or thermal spray & fusing techniques. Each technique has its own set of disadvantages. For example, thermal spray coatings may suffer from spalling, cracking, or de-lamination during processing because these coatings are only mechanically bound together and are not strong enough for heavy processes, such as aggregate or heavy ore operations. Also, plating large scale vessels or rollers is impractical, expensive, and environmentally intolerable. Further, plated vessels and rollers are not susceptible to efficient field repair.
Despite their deficiencies, welding or thermal spray & fusing are the methods of choice for treating surfaces. One challenge in hardfacing with welding or spray & fuse techniques lies in generating a surface that is hard enough to resist wear, yet not so hard that the weldment is so brittle that it cracks on either cooling after welding or under load when the roller is put to use. Because of repairability challenges, the compromises made to prevent catastrophic failure due to cracking and spalling result in less than optimal wear. Many different solutions have been developed by users and manufacturers of such industrial processing equipment to overcome these limitations, but many disadvantages remain.
For example, U.S. Pat. No. 4,848,683 to Kawatsu discloses a roller with two types of blocks which differ in wear resistance and which are arranged alternatively. As illustrated in Kawatsu, the body of the roller wears as it is used. Consequently, a fracture in the surface of the roller can propagate throughout the roller body. Even if such a fracture does not destroy the roller body completely, the roller body must be taken out of service and the fracture repaired, if repair is even possible.
U.S. Pat. No. 5,269,477 to Buchholtz et al. discloses a roller with embedded wear-resistant members of a material harder than the roller surface. As with Kawatsu, the roller body is not protected from fracture, necessitating costly and time-consuming repair. Further, a fracture in one wear-resistant member can destroy that member, reducing the efficacy of the roller and exposing the body of the roller to further damage.
Canadian Patent Application 2,202,213 to Patzelt el al. discloses a roller with pin-shaped profiled bodies embedded therein. As above, the body of the roll is not protected from wear. As noted in Patzelt, repair of the roll surface necessitates disassembling the roll, partially removing the roll material, and rebuilding the roll surface. Such a repair process requires considerable time and expense.
U.S. Pat. No. 6,523,767 to Ramesohl discloses roller inserts which can be replaced when worn. An embodiment of Ramesohl includes additional “lamellae” between the inserts to protect the roller body. However, these lamellae are also subject to wear and, moreover, reduce the total surface area of wear-resistant material, thereby reducing the efficacy of the roller. Also, as with Kawatsu, a fracture in one wear-resistant member can destroy that member, further reducing the efficacy of the roller and exposing the body of the roller to damage.
In light of the problems in the prior art, what is needed is a wear-resistant assembly that can be field repaired quickly and inexpensively.